str() prints first no matter the order in R - r

Question

I am writing a function that would give the dim() and str() of a given dataset.
JustfunFun <- function(.csv) {
csv <- read.csv(.csv)
dimVal <- dim(csv)
print("The dimension of the dataset is:")
strVal <- str(csv)
print("The structute of the dataset is:")
headVal <- head(csv)
return(list(dimVal, strVal, headVal))
}
Ideally, the output must have the dimension first, the structure second and then the head of dataset.
But the output is as follows:
> JustfunFun("tips.csv")
[1] "The dimension of the dataset is:"
'data.frame': 244 obs. of 8 variables:
$ obs : int 1 2 3 4 5 6 7 8 9 10 ...
$ totbill: num 17 10.3 21 23.7 24.6 ...
$ tip : num 1.01 1.66 3.5 3.31 3.61 4.71 2 3.12 1.96 3.23 ...
$ sex : Factor w/ 2 levels "F","M": 1 2 2 2 1 2 2 2 2 2 ...
$ smoker : Factor w/ 2 levels "No","Yes": 1 1 1 1 1 1 1 1 1 1 ...
$ day : Factor w/ 4 levels "Fri","Sat","Sun",..: 3 3 3 3 3 3 3 3 3 3 ...
$ time : Factor w/ 2 levels "Day","Night": 2 2 2 2 2 2 2 2 2 2 ...
$ size : int 2 3 3 2 4 4 2 4 2 2 ...
[1] "The structute of the dataset is:"
[1] "The head of the dataset is:"
[[1]]
[1] 244 8
[[2]]
NULL
[[3]]
obs totbill tip sex smoker day time size
1 1 16.99 1.01 F No Sun Night 2
2 2 10.34 1.66 M No Sun Night 3
3 3 21.01 3.50 M No Sun Night 3
4 4 23.68 3.31 M No Sun Night 2
5 5 24.59 3.61 F No Sun Night 4
6 6 25.29 4.71 M No Sun Night 4
>
How do I tackle this problem?

Answer 1

str, like print does not return anything. You can see the last line of utils:::str.default. The easiest way to see this is try to nest a str ( ie. str(str(mtcars)) ).
This function should print the way you want, AND store the data.
JustfunFun <- function(.csv) {
csv <- read.csv(.csv)
dimVal <- dim(csv)
print("The dimension of the dataset is:")
print(dimVal)
print("The structute of the dataset is:")
strVal <- utils:::capture.output(str(csv))
print(strVal)
print(head(csv))
return(invisible(list(dimVal, strVal, head(csv))))
}
Example:
write.csv(mtcars, "mtcars.csv", row.names = FALSE)
a <- JustfunFun("mtcars.csv")
Result:
[1] "The dimension of the dataset is:"
[1] 32 11
[1] "The structute of the dataset is:"
[1] "'data.frame':\t32 obs. of 11 variables:"
[2] " $ mpg : num 21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ..."
[3] " $ cyl : int 6 6 4 6 8 6 8 4 4 6 ..."
[4] " $ disp: num 160 160 108 258 360 ..."
[5] " $ hp : int 110 110 93 110 175 105 245 62 95 123 ..."
[6] " $ drat: num 3.9 3.9 3.85 3.08 3.15 2.76 3.21 3.69 3.92 3.92 ..."
[7] " $ wt : num 2.62 2.88 2.32 3.21 3.44 ..."
[8] " $ qsec: num 16.5 17 18.6 19.4 17 ..."
[9] " $ vs : int 0 0 1 1 0 1 0 1 1 1 ..."
[10] " $ am : int 1 1 1 0 0 0 0 0 0 0 ..."
[11] " $ gear: int 4 4 4 3 3 3 3 4 4 4 ..."
[12] " $ carb: int 4 4 1 1 2 1 4 2 2 4 ..."
mpg cyl disp hp drat wt qsec vs am gear carb
1 21.0 6 160 110 3.90 2.620 16.46 0 1 4 4
2 21.0 6 160 110 3.90 2.875 17.02 0 1 4 4
3 22.8 4 108 93 3.85 2.320 18.61 1 1 4 1
4 21.4 6 258 110 3.08 3.215 19.44 1 0 3 1
5 18.7 8 360 175 3.15 3.440 17.02 0 0 3 2
6 18.1 6 225 105 2.76 3.460 20.22 1 0 3 1
str(a)
$ : int [1:2] 32 11
$ : chr [1:12] "'data.frame':\t32 obs. of 11 variables:" " $ mpg : num 21 21 22.8 21.4 18.7 18.1 14.3 24.4 22.8 19.2 ..." " $ cyl : int 6 6 4 6 8 6 8 4 4 6 ..." " $ disp: num 160 160 108 258 360 ..." ...
$ :'data.frame': 6 obs. of 11 variables:
..$ mpg : num [1:6] 21 21 22.8 21.4 18.7 18.1
..$ cyl : int [1:6] 6 6 4 6 8 6
..$ disp: num [1:6] 160 160 108 258 360 225
..$ hp : int [1:6] 110 110 93 110 175 105
..$ drat: num [1:6] 3.9 3.9 3.85 3.08 3.15 2.76
..$ wt : num [1:6] 2.62 2.88 2.32 3.21 3.44 ...
..$ qsec: num [1:6] 16.5 17 18.6 19.4 17 ...
..$ vs : int [1:6] 0 0 1 1 0 1
..$ am : int [1:6] 1 1 1 0 0 0
..$ gear: int [1:6] 4 4 4 3 3 3
..$ carb: int [1:6] 4 4 1 1 2 1

Answer 2

Everything that you have written in your function is correct except the fact that you need to capture the strby command capture.output. So, below is the function that you are looking for:
JustfunFun <- function(.csv) {
csv <- read.csv(.csv)
dimVal <- dim(csv)
strVal <- capture.output(str(csv))
headVal <- head(csv)
return(list("The dimension of the dataset is:" = dimVal,
"The structute of the dataset is:" = strVal,
headVal))
}
Cheers & happy R Coding

Answer 3

If you are only interested in displaying the result without storing it, you could write a function that does not return anything but print the dimensions, the structure and the head of the data. The following code seems to do the trick.
# Simulation of the data
dat <- data.frame(obs=1:100,totbill=round(100*runif(100)),sex=sample(c("F","M"),100,replace=TRUE))
# Function
dim.str.head <- function(dat){
print("The dimension of the dataset is:")
print(dim(dat))
print("The structure of the dataset is:")
print(str(dat))
print("The first observations look like this:")
head(dat)
}
# Try the function
dim.str.head(dat)